1. Field of the Invention
This invention relates to container closures and, more particularly, to a plastic bottle cap.
2. Description of the Prior Art
Bottle caps, particularly bottle caps for consumable beverages, must have certain identifiable features. These are durability, inexpensiveness, ability to retain pressure, particularly where the beverage is carbonated, and a tamper-proof feature. In order to provide such inexpensive caps with tamper-proof features, it has been a known practice to utilize caps having integral tear strips which must be removed to allow the cap to be removed from the bottle neck. It is also known to have portions depending from the skirt which can be deformed over an outer rib on the bottle neck such that the portion must be either broken away from the skirt, or, in metal tops, circumferentially serrated upon removal of the cap.
Certain disadvantages have arisen in the use of such caps. In those instances utilizing plastic caps having portions depending from the skirt which are adapted to be separated from the skirt upon removal of the cap, there are both disadvantages in requiring an extra step to constrict the portion around the bottle rib after the cap is threaded onto the bottle and, in some instances, particularly with the elderly, the strength necessary to cause separation may be so great as to become a disadvantage. Further, in connection with metal caps, the strength necessary to cause the opening of the circumferentially spaced serrations may also be disadvantageous for certain people, particularly the elderly, and in other instances, can be so great as to strip the threads of the metal cap prior to the serrations being opened. Additionally, the plastic strip remaining on the bottle is unsightly and, when using metal tops, the resultant serrated metal edge can be a source of injury.
It has been suggested to provide a plastic bottle cap having an outer skirt for engaging the outer wall of the bottle neck and an inner skirt for engaging the inner wall of the bottle neck. In such a construction, as shown in U.S. Pat. No. 4,206,852, the bottle cap consists of an outer skirt, an axial end wall having a peripheral portion adjacent the outer skirt, the peripheral portion terminating in a first inner depending skirt extending downwardly substantially parallel with the outer skirt, a second inner skirt extending upwardly and a connecting portion connecting the two inner skirts. A central disc shaped land is formed inwardly of the second inner skirt. In such a construction the central land is not movable with respect to the peripheral land of the axial end.
It would therefore be an advance in the art to provide a bottle cap having an anti-tamper feature which allows easy recognition of a previously opened bottle, which cap also has advantages of strength, economics of production and ability to retain a seal under pressure.